Mechanism of antibacterial phytoconstituents: an updated review.

The increase of multiple drug resistance bacteria significantly diminishes the effectiveness of antibiotic armory and subsequently exaggerates the level of therapeutic failure. Phytoconstituents are exceptional substitutes for resistance-modifying vehicles. The plants appear to be a deep well for the discovery of novel antibacterial compounds. This is owing to the numerous enticing characteristics of plants, they are easily accessible and inexpensive, extracts or chemicals derived from plants typically have significant levels of action against infections, and they rarely cause serious adverse effects. The enormous selection of phytochemicals offers very distinct chemical structures that may provide both novel mechanisms of antimicrobial activity and deliver us with different targets in the interior of the bacterial cell. They can directly affect bacteria or act together with the crucial events of pathogenicity, in this manner decreasing the aptitude of bacteria to create resistance. Abundant phytoconstituents demonstrate various mechanisms of action toward multi drug resistance bacteria. Overall, this comprehensive review will provide insights into the potential of phytoconstituents as alternative treatments for bacterial infections, particularly those caused by multi drug resistance strains. By examining the current state of research in this area, the review will shed light on potential future directions for the development of new antimicrobial therapies.

Characterization of blaOXA-48-carrying plasmids and small non-AMR-coding plasmids collected from Ukrainian patients.

PURPOSE: Carbapenemase-producing Enterobacterales (CPE) pose a serious threat for healthcare facilities worldwide, yet the mode of transmission is often unclear. Recently, we recorded an increase of blaOXA-48-harboring isolates at our hospital associated with patients with previous medical treatment in the Ukraine. We used long-read whole genome sequencing (lrWGS) to characterize these isolates including their plasmids. METHODS: Samples were collected as part of clinical routine diagnostic or screening of multi-drug resistance bacteria (MDRB). Antimicrobial susceptibility testing was performed and all MDRB (n = 10) were sequenced by lrWGS for genotyping, identification of antimicrobial resistance (AMR) genes, and characterization of plasmids. RESULTS: While routine analysis of core genome multilocus sequence typing (cgMLST) did not show any genetic similarities between isolates, we found an unexpected high similarity in the plasmid diversity of different Enterobacterales in patients with previous medical treatment in the Ukraine. This included an IncL/M plasmid carrying blaOXA-48 and additional small non-AMR-coding plasmids. CONCLUSION: Our results show that lrWGS can be used in the routine setting to uncover similarities in plasmids and may give further information about potential epidemiologic associations. In the future, analysis of both AMR and non-AMR plasmids may provide an additional layer of information for molecular surveillance of CPE.

Multidrug-Resistant Bacteria Colonization in Patients Admitted to Dr. Cipto Mangunkusumo Hospital Jakarta, Indonesia.

BACKGROUND: Antibiotic resistance is the main problem in infectious disease management. Multidrug-resistant (MDR) bacteria could be carried by admitted patients and become a source of spread in the hospital, causing infections in other patients or the patients themselves. However, the screening of MDR bacteria has not been a standard in developing countries. This study aimed to get the prevalence of MDR bacteria colonization in patients on admission to Dr. Cipto Mangunkusumo Hospital. METHODS: Selective liquid media with added antibiotics were used for culturing the MDR bacteria. While admitted to the hospital, subjects were sampled and interviewed to fill out a questionnaire. The screening specimens used for this study were throat, navel, rectal, nasal, and armpit swabs. During hospitalization, hospital-acquired infections (HAIs) were recorded. RESULTS: Of 100 patients included in the study, the prevalence of MDR bacteria colonization on admission was 63% (n=63) with the prevalence of CR-GNB, ESBL-PE, and MRSA were 11%, 54%, and 11%, respectively. Two-thirds of the patients with HAIs (n=8/12) were colonized with MDR bacteria. Factors associated with MDR bacteria colonization were the recent use of invasive medical devices and comorbidity, while a factor associated with CR-GNB colonization was the recent use of antibiotics. CONCLUSION: The prevalence of MDR bacteria colonization in patients on admission to Dr. Cipto Mangunkusumo Hospital in 2022 was 63% (n=63), of which 12.68% (n=8) experienced HAIs during hospitalization. MDR bacteria colonization was associated with the recent use of invasive medical devices and comorbidity. History of antibiotic use was associated with CR-GNB colonization.

Current synthetic chemistry towards cyclic antimicrobial peptides.

Antimicrobial peptides (AMPs) have great potentials for developing novel antibiotics against multi-drug resistant (MDR) bacteria. However, the clinical application of AMPs is limited due to their poor protease stability and high hemolytic toxicity. Various strategies have been widely explored to improve the pharmacological properties of natural or artificial antimicrobial peptides, including D- or non-natural amino acid residue replacement, backbone modification, cyclization, PEGlytion, and lipidation. Among others, peptide cyclization, which has been widely applied to enhance the biostability and target selectivity of bioactive peptide, is a very appealing and promising strategy for developing novel antibiotics based on AMPs. Herein, we summarize the current strategies for synthesizing cyclic antimicrobial peptides and the resulting influence of peptide cyclization on the biological activities.

Biologically synthesized copper oxide nanoparticles enhanced intracellular damage in ciprofloxacin resistant ESBL producing bacteria.

Copper oxide nanoparticles (CuO NPs) were synthesized biologically using leaf extract of Camilla japonica. The typical UV-visible spectral peak of CuO NPs was observed at a wavelength of ∼290 nm, which confirmed their successful synthesis. From scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses, the synthesized CuO NPs were found to possess spherical shape. Energy dispersive X-ray analyzer (EDX) results revealed that the CuO NPs are almost pure with atomic percentages of 50.92 for Cu and 49.08 for O. Fourier transform infrared (FTIR) confirmed the presence of an absorption peak located at a wavenumber position of ∼480 cm-1 typical for highly pure CuO NPs. TEM images displayed that the particles are relatively uniform in size ∼15-25 nm. The P. aeruginosa and K. pneumonia showed complete resistance against Hexa 077 antibiotic discs. The result of ≤22 ceftazidime and ≤27 cefotaxime confirmed that both the uropathogens were ESBL producers. The ≥8 mm of the MIC stripe further confirmed that both the uropathogens were ESBL producers. Furthermore, the antibacterial activity of CuO NPs against selected ESBL producing P. aeruginosa and K. pneumoniae at minimum inhibition concentration (MIC) of 100 µg/mL. The decreased cell viability and damaged membrane construction of both the uropathogens were observed by confocal laser scanning microscope (CLSM) using AO/EB stains at desired MIC dose. The morphological damage of the bacterial cells was demonstrated by SEM analysis. Hence, based on the above in vitro findings, the results suggested that the CuO NPs are efficient antibacterial compounds against ESBL producing bacteria, and that the plant leaf mediated CuO NPs can be considered as novel and promising material to act against various infectious bacteria.

Antibacterial activity and modes of action of phosvitin-derived peptide Pt5e against clinical multi-drug resistance bacteria.

Pt5e, a mutant peptide derived from the C-terminal 55 residues of zebrafish phosvitin, has been suggested to be a novel antibacterial peptide. However, if it is applicable to clinical MDR bacteria remains to be tested. In this study, high-purity Pt5e was first expressed and purified by fusion with cationic elastin-like polypeptide. Pt5e was then shown to be capable of effectively killing all the five clinical MDR bacteria tested. Pt5e kill the MDR bacteria at several levels, including inserting into the bacterial membranes, causing the membrane depolarization and permeabilization, and inducing the intracellular apoptosis/necrosis. All these data suggest that Pt5e is a promising therapeutic potential as an antibiotics against clinical MDR bacteria.

Plant-based Natural Products as inhibitors for Efflux Pumps to Reverse Multidrug Resistance in Staphylococcus aureus: A Mini Review.

Wounds provide a favourable site for microbial infection. Wound infection makes the healing more complex and does not proceed in an orchestrated manner leading to the chronic wound. Clinically infected wounds require proper antimicrobial therapy. Broad-spectrum antibiotics are usually prescribed first before going to targeted therapy. The current conventional mode of therapy mainly depends on the use of antibiotics topically or systemically. Repeated and prolonged use of antibiotics, however, leads to multidrug resistance. Staphylococcus aureus is the most common multidrugresistant microorganism found in wounds. It effectively colonizes the wound and produces many toxins, thereby reducing the host immune response and causing recurrent infection, thus making the wound more complex. The overexpression of efflux pumps is one of the major reasons for the emergence of multidrug resistance. Inhibition of efflux pumps is, therefore, a potential strategy to reverse this resistance. The effective therapy to overcome this antibiotic resistance is to use combination therapy, namely the combination of an inhibitor, and a non-antibiotic compound with an antibiotic for their dual function. Many synthetic efflux pump inhibitors to treat wound infections are still under clinical trials. In this connection, several investigations have been carried out on plant-based natural products as multidrug resistance-modifying agents as they are believed to be safe, inexpensive and suitable for chronic wound infections.

Acyldepsipeptide Analogues: A Future Generation Antibiotics for Tuberculosis Treatment.

Acyldepsipeptides (ADEPs) are a new class of emerging antimicrobial peptides (AMPs), which are currently explored for treatment of pathogenic infections, including tuberculosis (TB). These cyclic hydrophobic peptides have a unique bacterial target to the conventional anti-TB drugs, and present a therapeutic window to overcome Mycobacterium Tuberculosis (M. tb) drug resistance. ADEPs exerts their antibacterial activity on M. tb strains through activation of the protein homeostatic regulatory protease, the caseinolytic protease (ClpP1P2). ClpP1P2 is normally regulated and activated by the ClpP-ATPases to degrade misfolded and toxic peptides and/or short proteins. ADEPs bind and dysregulate all the homeostatic capabilities of ClpP1P2 while inducing non-selective proteolysis. The uncontrolled proteolysis leads to M. tb cell death within the host. ADEPs analogues that have been tested possess cytotoxicity and poor pharmacokinetic and pharmacodynamic properties. However, these can be improved by drug design techniques. Moreover, the use of nanomaterial in conjunction with ADEPs would yield effective synergistic effect. This new mode of action has potential to combat and eradicate the extensive multi-drug resistance (MDR) problem that is currently faced by the public health pertaining bacterial infections, especially TB.

Reactive organic radical-doped Ag(I)-based coordination compounds for highly efficient antibacterial wound therapy.

Antibiotics, being critical antimicrobial agents, have been widely used for treating bacterial infections. However, prolonged use of antibiotics can induce drug resistance resulting in "superbug" that threatens human health. Therefore, developing antibiotic-free materials with intrinsic antibacterial properties is the key to the "superbug" challenge. In this study, two highly efficient metal-organic frameworks (MOFs) were successfully assembled through synergistic use of the antibacterial properties of reactive organic radicals and silver (Ag) cations. These hybrid Ag-based materials possessed radical-doped characteristics, continuously releasing Ag+, which significantly inhibited the growth of four common Gram-negative and Gram-positive human pathogens (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus), and particularly two multi-drug-resistance bacteria (MRSA and MDR-PA). Furthermore, in vivo assays indicated that the synergistic antibacterial effect of these compounds could significantly accelerate the healing rate of infected wounds in mice. Blood biochemistry and histological analyses of main organs in treated mice also exhibited negligible cytotoxicity. This study unveiled the promising potential of Ag-MOFs for anti-infective therapies and future clinical applications.

Morpholinium-based ionic liquids show antimicrobial activity against clinical isolates of Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a multi-drug resistant (MDR) pathogen. It is classified by WHO as one of the most life-threatening pathogens causing nosocomial infections. Some of its clinical isolates and their subpopulations show high persistence to many antibiotics that are recommended by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Thus, there is a need for non-traditional classes of antibiotics to fight the increasing threat of MDR P. aeruginosa. Ionic liquids (IL) are one such promising class of novel antibiotics. We selected four strains of P. aeruginosa and studied the growth inhibition and other effects of 12 different ILs. We used the well-characterized P. aeruginosa PAO1 (ATCC 15692) as model strain and compared it to three other isolates from chronic lung infection (LES B58), skin burn infection (UCBPP-PA14) and keratitis infection (39016), respectively. The ILs consisted of either 4,4-didecylmorpholinium [Dec2Mor]+ or 4-decyl-4-ethylmorpholinium [DecEtMor]+ cations combined with different anions. We found that the ILs with 4,4-didecylmorpholinium [Dec2Mor]+ cations most effectively inhibited bacterial growth as well as reduced strain fitness and virulence factor production. Our results indicate that these ILs could be used to treat P. aeruginosa infections.

Estimation of the Difference in Colistin Plasma Levels in Critically Ill Patients with Favorable or Unfavorable Clinical Outcomes.

In recent decades, antimicrobial resistance (AMR) has led to an increased use of therapeutic alternatives. Among these options, colistin continues to be an option for the treatment of multi-resistant (MDR) Gram-negative bacterial infections. However, due to its high toxicity (nephrotoxicity and neurotoxicity) and narrow therapeutic window, colistin treatment must be utilized carefully. Colistin-treated patients have been observed to have higher mortality due to inadequate therapeutic levels. The objective of this study was to estimate the difference in colistin plasma levels in critically ill patients, and its relationship to favorable or unfavorable clinical outcomes. This prospective observational study was conducted between September 2017 and June 2020 at the Universidad de La Sabana Clinic, in patients who had been treated with colistimethate sodium (CMS) for at least 72 h until day 7 of drug treatment in the critical care unit of a university hospital. There were no statistically significant differences in colistin levels between groups with favorable or unfavorable clinical outcomes (0.16 SD vs. 0.54 SD p-value = 0.167). There was higher mortality in patients with subtherapeutic levels (18% vs. 0%), and additionally, there was a greater rate of renal failure in the group with higher therapeutic levels (50% vs. 20.7%). Due to the loss of power of the study, we were unable to demonstrate a possible difference between colistin levels related to favorable or unfavorable clinical outcomes at day 7. However, we recommend further studies to evaluate the impact of measuring levels in terms of mortality and security.

Enhancing azithromycin antibacterial activity by encapsulation in liposomes/liposomal-N-acetylcysteine formulations against resistant clinical strains of Escherichia coli.

E. coli is an Enterobacteriaceae that could develop resistance to various antibiotics and become a multi-drug resistant (MDR) bacterium. Options for treating MDR E. coli are limited and the pipeline is somewhat dry when it comes to antibiotics for MDR bacteria, so we aimed to explore more options to help in treating MDR E. coli. The purpose of this study is to examine the synergistic effect of a liposomal formulations of co-encapsulated azithromycin and N-acetylcysteine against E. coli. Liposomal azithromycin (LA) and liposomal azithromycin/N-acetylcysteine (LAN) were compared to free azithromycin. A broth dilution was used to measure the MIC and MBC of both formulations. The biofilm reduction activity, thermal stability measurements, stability studies, and cell toxicity analysis were performed. LA and LAN effectively reduced the MIC of E. coli SA10 strain, to 3 µg/ml and 2.5 µg/ml respectively. LAN at 1 × MIC recorded a 93.22% effectiveness in reducing an E. coli SA10 biofilm. The LA and LAN formulations were also structurally stable to 212 ± 2 °C and 198 ± 3 °C, respectively. In biological conditions, the formulations were largely stable in PBS conditions; however, they illustrated limited stability in sputum and plasma. We conclude that the formulation presented could be a promising therapy for E. coli resistance circumstances, providing the stability conditions have been enhanced.

Characterization of synergistic antibacterial effect of silver nanoparticles and ebselen.

The emerging and spreading of multi-drug resistant (MDR) bacteria have been becoming one of the most severe threats to human health. Enhancing oxidative stress as mimicking immune system was considered as a potential strategy to fight against infection of MDR bacteria. In this study, we investigated the antibacterial efficiency of such a strategy which combines silver nanoparticles (AgNPs) with ebselen. The results showed that AgNPs and ebselen combination had significant synergistic killing effects both on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in vitro, including model strains of China Veterinary Culture Collection and MDR clinical isolates, which is similar as the combination of silver ion and ebselen. AgNPs exhibited to be a strong inhibitor of bacterial thioredoxin reductase, same as a free silver ion. Ebselen mitigated the cytotoxicity of AgNPs to HeLa cells. However, in a bacteria-cell coexistence condition, the synergistic bactericidal effect was only observed on S. aureus (p<.05), while the temporary synergistic inhibitory effect on E. coli within 4 hours treatment (p<.01). In mice infection model, a combination of AgNPs and ebselen did not increase protection against the challenge of clinical E. coli CQ10 strain. Our data demonstrated that AgNPs and ebselen combination may be a promising strategy to fight against the increasingly MDR bacteria targeting bacterial thiol redox system.

Vancomycin Capped with Silver Nanoparticles as an Antibacterial Agent against Multi-Drug Resistance Bacteria.

Purpose: Many antimicrobial medications are available to combat infections. However, the indiscriminate use of antibiotics has produced antibiotic resistance in the case of many bacterial pathogens. This study focuses on the development of nanoparticles (NPs) that enhance the in vitro antibiotic activity of vancomycin against multi-drug resistant (MDR) organisms. Methods: Spherical shaped thioglycolic acid-stabilized silver nanoparticles (TGA-AgNPs) were prepared by using a simple chemical reduction method. Then, vancomycin was conjugated to the terminal carboxyl of TGA in the presence of N-Hydroxysuccinimide (NHS) and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC). Afterwards, the antibacterial activity of these nanoconjugates was examined by using the minimum inhibitory concentration (MIC) assay against MDR bacteria. Results: The rate of vancomycin bound to the AgNPs was 19.6%. The MIC values of vancomycin (Van)-capped AgNPs against tested pathogens were in the range of (3.2, 1.6, 0.8, 0.4, 0.2, 0.1, 0.05, and 0.025 µl/ml). The MIC was 0.1 µg/ml for VRE, MIC≤0.02 µg/ml for MRSE, and 0.05 µg/ml for S. aureus. The MIC corresponded to the MBC for all bacterial species. Conclusion: This study indicated that some antimicrobial agents like vancomycin can be conjugated with AgNPs. This can lead to increased antimicrobial activity against MDR microorganisms.